Due to the lack of a direct acting force or a torque, system control of an underactuated system generally tends to be difficult. For example, a unicycle robot may have only one wheel contacting the ground and an ordinary wheel is only capable of forward and backward movement, so the unicycle robot cannot provide a lateral torque while the veer of the unicycle robot needs a torque. Likewise, a satellite, a spacecraft and a missile all need to be driven by a torque in order to point to a predetermined direction. An advanced spacecraft and a missile generally realize attitude adjustment through outward gas ejection, and the satellite may use inertial flywheel rotation for generating a reaction wheel and a magnetic torque or a liquid loop so as to realize attitude adjustment. The main propeller reverse torque overcoming of a helicopter or a saucer aircraft is realized by adopting a rotating tail propeller that is orthogonal to a main propeller.
Certain existing approaches utilize a scheme of controlling lateral balance of a unicycle robot by an inertial flywheel. One other approach utilizes a scheme of controlling lateral veer of a unicycle robot by an inertia flywheel. The method of using an inertia flywheel to provide a reverse torque is also widely employed in satellite attitude adjustment, although it is difficult to use an inertia flywheel providing reverse torque to control attitude. The reason is that the magnitude of the reverse torque provided by an inertia flywheel is in direct ratio to rotational acceleration of the flywheel while a motor is a speed servo system for which tracking for acceleration is not easy to achieve when the flywheel rotates at a uniform speed, and thus no reverse torque is generated. In addition, the magnitude of the provided reverse torque is limited because of the limitation of the rotational speed of the motor.
One technique, as disclosed in Chinese Patent Application No. 200510111490.3, provides a method and system for controlling attitude of micro-satellite based on an active magnetic control, mainly by adopting magnetic torque active magnetic control, integrating with gravity gradient rod and momentum wheel offset stabilization control unit to form satellite attitude stabilization platform, and utilizing coil current interaction on the geomagnetic field and a satellite to provide a torque to adjust satellite attitude. Such technique is significantly different from that of the present invention in that the interaction between a permanent magnet and an armature winding in the magnetic field are utilized to generate a counter torque. On the other hand, according to the technique as disclosed in Chinese Patent Application No. 200910152010.6, an angular momentum produced through liquid flowing in a pipe enables the satellite attitude to change. However, such technique is also significantly different from that of the present invention in a scheme that electromagnetic effect is used to adjust satellite attitude. For a spacecraft, the carried gas capable of being jetted out is limited, while the scheme where electrical energy is converted into mechanical energy can utilize inexhaustible solar energy.
A technique, as disclosed in Chinese Patent Application Nos. 200720037988.4 and 200820120359.2, uses everyday objects to complete many experiments of motor-driven electromagnet generation principle, eddy current working principle, eddy current generation effect and eddy current generating torque under magnetic field effect. Another technique, as disclosed in Chinese Patent Application No. CN102529574A, provides a mobile medical equipment truckle with an electromagnetic torque balance motor installed, wherein the technique can use friction torque of electromagnetic torque balance truckle generated by the rotation of the truckle, to reduce thrust for the working staff. Yet another technique, as disclosed in Chinese Patent Application No. CN1532656A, provides a miniature three-shaft attitude control device, including three planar motors, a cube support frame and a control plate, wherein the planar motors include rotors, stators, rotor shafts and bearings. The rotors comprise a plurality of pairs of magnetic poles. The planar motors are disposed on three mutually perpendicular planes of the cube support frame through the rotor shafts and the bearings. Because stator coils in the stators are secured on a substrate, and a flat stator is in a fixed state, the direction of reactive force applied on the rotors is opposite to direction of the force applied on the stators. The stator coils are continuously made to pass through three-phase square wave current according to a certain electrifying sequence, that is, continuous rotation of the rotors is guaranteed. Such a structure ensures larger rotating torques of the motors. Still another technique, as disclosed in Chinese Patent Application No. CN1983098A, provides a micro satellite attitude control system containing a magnetorquer, wherein the magnetorquer is formed by three magnetic bars and its power amplifier circuit. When current passes through the magnetic bars, controllable magnetic torque, which can react with the ground magnetic field to generate three-shaft control torque, can be generated. A control system with active magnetic control by the magnetorquer as the core and in combination with gravity gradient rod and momentum wheel offset stabilization works as a satellite attitude stabilization platform.